The human larynx has three basic functions that can be described as follows: deglutition (swallowing), respiration, and phonation (voice). Its most important part from a functional point of view is the crico-arytenoideus unit, which consists of the following:                the fibrous cartilage structure constituted by the cricoid cartilage, the arytenoid cartilage, and the crico-arytenoideus articulation together with its capsule.        muscle apparatus constituted by the crico-arytenoideus posticus and lateralis muscle.        a vascular-nerve apparatus constituted by the recurrent nerve and the posterior inferior laryngeal artery.        a flat cover consisting of the arytenois mucous membrane.        
In particular, the cricoid is a rigid, ring-shaped cartilaginous structure; and the arytenoid is a rigid, triangular cartilaginous structure situated above the cricoid cartilage and articulated with it, forming the crico-artenoideus unit.
The three primary functions of the larynx are based on the aforecited elements:                Respiration is provided by the rigid, ring-shaped cricoid cartilage.        Phonation (voice) is obtained by the production of sounds that originate in the windpipe through which air is expirated situated at the base of the tongue and the arytenoid.        Deglutition (swallowing) is accomplished by the sphincteral action of the arytenoid unit, provided that the tongue retropulsion and larynx elevation functions remain intact.        
The most common health conditions that lead to the need for surgery to remove the larynx, in whole or in part, involve tumors.
Restoration in an artificial manner of the physiological functions associated with the larynx that has been removed represents an objective that for over a century has challenged otorhinolaryngologists. Ever since 1876, recourse has been made to ablation of the stoma (opening) which, by its very nature, represents the greatest limit to social re-integration of a patient who has undergone a total laryngectomy.
In 1956 (I. De Vincentiis, “Ulteriori risultati della sostituzione della laringe nel cane,” Min O.R.L. 6, 260, 1956; I. De Vencentiis and M. De Santis, “La réplacement du larynx chez le chien avec prothèse composeé,” Ann. Otoirayng. 73, 57, 1956) experiments were conducted on a dog, replacing its larynx with a polyethylene tube reinforced externally with steel and Vitallium wires or threads. At a later time (I. De Vincentiis, “Primi tentativi della sostituzione della laringe nell'uomo,” Arch. Ital O.R.L. 81, 355, 1970; I. De Vincentiis, D. Tropodi, G. lannetti. R. Filippo, A. Bisemi, “La sostituzione della laringe dell'uomo,” Valsalva 47.1.1971), a first effort was made to use a prosthetic replacement of a human larynx, using a white dacron tube reinforced with Vitallium rings. However, the swallowing difficulties that ensued made it necessary, after little more than a month, to proceed to a conventional, total laryngectomy.
In recent years, surgery of the larynx has evolved considerably from an approach based on demolition to one that is more conservative. Functional laryngeal surgery involves a whole series of operating techniques, put into practice in case of neoplastic disease, aimed at preserving the functions of the vocal organ to the greatest extent possible. In cases of neoplastic disease, functional laryngeal surgery is identified with the techniques of partial and sub-total laryngectomy. The objective of sub-total surgery is to obtain a “neo-larynx” that is valid from a functional standpoint. This means rebuilding a new vocal organ that is capable of carrying out the three vital functions of the larynx, i.e., respiration, deglutition, and phonation.
The surgical techniques of sub-total laryngectomy, described in De Vincentiis et al., “Supracricoid Laryngectomy with Cricohyoidopexy (CHP) in the Treatment of Laryngeal Cancer: A Functional and Oncological Experience,” Laryngoscope 106:1108-1114, 1996, involve the following:                Subtotal laryngectomy with preservation of two-thirds of the epiglottis and one or both arytenoid cartilages: Crico-hyoido-epiglotto-pexy (CHEP) according to Mayer-Piquet, which represents an alternative to partial surgery.        Subtotal laryngectomy with preservation of one or both arytenoid cartilages: Crico-hyoido-pexy (CHP), according to Labayle, which represents an alternative to total surgery.        
Both of the foregoing techniques call necessarily for the preservation of both the cricoid ring and at least one of the arytenoid units, as these represent the minimum elements necessary for reconstruction of the crico-arytenoid unit and serve as the basis for the rehabilitation of patients who have undergone sub-total surgery.
The cornerstone of this reconstructive surgery is represented by the “crico-arytenoid unit”, on which a large part of the functional recovery of the neo-larynx is based.
From a surgical point of view, the maintenance of this structure is of primary importance. To this end, during surgery it is necessary to respect the vascular-nerve peduncle and the arytenoid mucous cap. Early mobilization of the arytenoid avoids the insurgence of a fibrosis of the crico-arytenoid articulation, which would lead to functional failure of the surgery and would require a total laryngectomy, not for oncological reasons but motived solely by the functional inadequacy of the neoglottis.
Movement of the crico-arytenoid unit, whose parts have been described above, takes place basically along two lines:
a) Vertical movement, caused by the crico-arytenoideus posticus muscle which, by pulling down and backward on the muscle apophysis, makes the arytenoid rotate in a circular movement upwards and outwards, opening the laryngeal neo-lumen. Relaxation of this muscle makes the arytenoid lean forward (a movement referred by Bonnet as the “arytenoid bow or nod”).b) Horizontal movement, caused by the lateral crico-arytenoideus muscle which, by pulling down and forward on the muscle apophysis, causes a rotation inwards of the arytenoid, leading to closure of the laryngeal lumen.
That closing movement of the neo-glottis is thus achieved by rotation of the arytenoid body forward, downward, and inward, as a result of contraction of the lateral crico-arytenoideus muscle and relaxation of the crico-arytenoideus posticus muscle. The opposite takes place for opening the neo-glottis (relaxation of the lateral crico-arytenoideus muscle and contraction of the crico-arytenoideus posticus muscle.
At the present time, thanks to progress made in surgical techniques and, even more particularly, to the public being made more aware about prevention, recourse to total laryngectomies is becoming less and less frequent. Nevertheless, there are still a significant number of patients for whom this operation becomes necessary. And in these cases, despite the contribution of modern rehabilitation techniques, it has not been possible to get satisfactory results in terms of social recovery of the patients. Indeed, even when:                resumption of deglutition (swallowing) is good;        resumption of phonation (voice function) can be obtained by creating phonic fistulas (air passage between the trachea and the esophagus, in some cases inserting a valve when there is incontinence during swallowing), or by training the patient to coordinate the vibration of the hypopharyngeal mucous produced by the air swallowed into the stomach (esophagal voice);it is nevertheless true that:        resumption of respiration by natural means still constitutes a problem. As a matter of fact, all efforts to connect the trachea directly to the base of the tongue have failed, because the posterior membranous part of the trachea is not rigid enough to sustain a lumen sufficiently wide for satisfactory respiratory function. It is therefore clear that, even though the procedure may apply to an ever smaller number of patients, the problems connected with total a laryngectomy have not been resolved.        
A study has now been made and an artificial laryngeal prosthesis designed that will make it to possible for patients who have undergone a total laryngectomy to recover socially and to overcome the problems described above.